POLYPARCI calculates confidence intervals for parameters estimated by ‘polyfit’.


Updated 18 Feb 2014

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POLYPARCI uses the procedures outlined in the ‘polyfit’ documentation to calculate the covariance matrix, and uses ‘betainc’ and ‘fzero’ to calculate the cumulative t-distribution and the inverse t-distribution for a given probability and degrees-of-freedom. It uses only core MATLAB functions and does not require the Statistics Toolbox.
The t-distribution and t-statistic calculations have a relative error of about 1E-012 compared to the Statistics Toolbox functions ‘tcdf’ and ‘tinv’. The relative error of the confidence intervals is about 1E-005 compared to those calculated by ‘nlinfit’ and ‘nlparci’ with the same model on the same data.

Cite As

Star Strider (2023). polyparci (https://www.mathworks.com/matlabcentral/fileexchange/39126-polyparci), MATLAB Central File Exchange. Retrieved .

MATLAB Release Compatibility
Created with R2013b
Compatible with any release
Platform Compatibility
Windows macOS Linux

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Version Published Release Notes

Update 02 2014 — Now works with 2013b. Corrected typo. Added internal documentation. Inverted CI output matrix to 2xN so columns correspond to elements in 1xN parameter vector returned by polyfit.